1. Field of the Invention
The present invention pertains to short circuit protection in hydrocarbon exploration and production electrical systems and, more particularly, short circuit protection for such electrical systems comprising serially connected nodes.
2. Description of the Related Art
Short circuit protection systems are familiar protections for electrical systems. A short circuit may create dangerous conditions. For example, a short circuit may cause dangerous electrical loads for equipment that may damage electrical/electronic components of equipment, thereby rendering them inoperable. Dangerous electrical loads arising from short circuit conditions may also cause fires and other dangerous situations. The ubiquity of electricity in modern life has therefore led to much interest in short circuit protections.
The standard way of solving short circuit situations is to implement a hierarchy of automatic fuses. Each fuse has a certain current rating. The fuse trips when the current exceeds its rating. For example in a house, the main fuse has a higher current rating than the fuse for each individual power domain. In addition electrical devices like radios or personal computers (“PCs”) may have an internal fuse as well, with lower current rating than the power domain it draws power from. The point with such a hierarchy is to reduce as much as possible the area that the short affects. This makes it easier to locate the problem and fix it while ensuring safety in the overall system. It also limits the area affected by the short.
These kinds of considerations take on more importance in some circumstances. A seismic survey system is typically laid out with a series of units connected together by a seismic cable in between. Cables, connectors and units transferring or relaying electrical power in a seismic survey system are subject to short circuit situations. There can be several hundred units in each power domain and 10 s of meters of cable between them, making the whole power domain span several kilometers. Thus, not only may there be a very large number of places in which a short circuit condition might occur, but they may be spread out over large distances. Locating and fixing a short circuit can therefore be a time consuming and difficult task.
In a seismic survey system, a hierarchy of automatic fuses such as that described above means that the power supply needs to include a fuse which will trip if there is a short anywhere on the line of sensors. The negative side of this solution is that the whole line of sensors loses power as long as there is a short anywhere on the line. It also is not possible to automatically know where on the line the short is, meaning it will take a long time to repair.
The present invention is directed to resolving, or at least reducing, one or all of the problems mentioned above.